An optical device includes at least one surface emitting laser device having a dielectric film for causing a central portion of a light emitting region to have a comparatively higher reflectivity than a peripheral portion; a light receiving element disposed, with respect to a first direction, on one side to the surface emitting laser device; and a transparent member disposed in a path of light emitted from the surface emitting laser device and configured to reflect a portion of the light toward the light receiving element as monitoring light. The central portion has shape anisotropy in which a width measured on a line extending in the first direction and passing through the center of the light emitting region is smaller than a width measured on a line extending in a second direction, which is perpendicular to the first direction, and passing through the center of the light emitting region.